for me it really depends on the stand i have some that are better at different times or weather conditions

If I could only choose one it would have to be evening for a couple reasons. The big boys move just before dark and most of them I've killed in the evening were walking like they were on a mission paying little or no attenion to what was going on around them. The other reason is that it would be hard for me to quit hunting in the morning or mid-day and go home. It would be easier to give it up for darkness......